Ctrl-<digit> doesn't usually set earmarks in 45 or 45.1
In earlier versions (e.g., 44) with a cell selected pressing a digit on the keyboard with the control key held down set an earmark for that number on the cell.
In versions 45 and 45.1 this usually doesn't work. If you ctrl-click to select the cell then it does work but if you just click (without control) or move to the cell using the cursor keys then ctrl- doesn't do anything. If you ctrl-click on a cell and set some earmarks then use the cursor keys to move to another cell then ctrl- doesn't work in the new cell but if you then use the cursor keys to move back to the cell where they worked then they continue to work there.
Personally, I only play using the keyboard, not the mouse (it's too slow), and I don't have the memory capacity to solve anything but the simplest puzzles without using earmarks so this bug makes the game unplayable for me.